Diode including a plurality of trenches

ABSTRACT

A diode is proposed. The diode includes a semiconductor body having a first main surface and a second main surface opposite to the first main surface. The diode further includes an anode region and a cathode region. The anode region is arranged between the first main surface and the cathode region. An anode pad area is electrically connected to the anode region. The diode further includes a plurality of trenches extending into the semiconductor body from the first main surface. A first group of the plurality of trenches includes a first trench electrode. A second group of the plurality of trenches includes a second trench electrode. The first trench electrode is electrically coupled to the anode pad area via an anode wiring line and the second trench electrode.

TECHNICAL FIELD

The present disclosure is related to a diode, in particular tosemiconductor devices including the diode.

BACKGROUND

Diodes are a key device element in integrated circuits (ICs). Forexample, during half-bridge turn-off of a semiconductor switch, aso-called freewheeling diode takes over the current. In order to enter alow resistive forward conducting mode, the freewheeling diode isrequired to bring its junction into forward bias and reduce the built-inblocking electric field. During this process, the freewheeling diode isnot yet flooded with charge carriers causing a large voltage drop whenforced to conduct significant current. As conductance increases whilecharge carriers are stored in the diode, this voltage drop reduces. Thephenomenon is characterized by the so-called forward recovery voltage.In circuit applications, the forward recovery voltage is a key parametersince a parallel switching device, e.g. an insulated gate bipolartransistor (IGBT), is required to have enough reverse blockingcapability to withstand this voltage peak. Moreover, a gate driver,which may drive the gate of the parallel switching device, can bedamaged if the forward recovery voltage becomes too large. Differenttypes of diodes have different levels of forward recovery voltage. Thismay depend on thickness, base-material-resistivity, anode efficiency andother factors. In case of a diode including trenches charging ofparasitic trench-related capacitances may cause a pro-longed forwardrecovery phase with larger amplitude of the forward recovery voltage.

There is a need to reduce the forward recovery voltage of diodesincluding trenches.

SUMMARY

An example of the present disclosure relates to a diode. The diodeincludes a semiconductor body having a first main surface and a secondmain surface opposite to the first main surface. The diode furtherincludes an anode region and a cathode region. The anode region isarranged between the first main surface and the cathode region. An anodepad area is electrically connected to the anode region. The diodefurther includes a plurality of trenches extending into thesemiconductor body from the first main surface. A first group of theplurality of trenches includes a first trench electrode. A second groupof the plurality of trenches includes a second trench electrode. Thefirst trench electrode is electrically coupled to the anode pad area viaan anode wiring line and the second trench electrode.

Another example of a diode according to the present disclosure includesa semiconductor body having a first main surface and a second mainsurface opposite to the first main surface. The diode further includesan anode region and a cathode region. The anode region is arrangedbetween the first main surface and the cathode region. An anode pad areais electrically connected to the anode region. The diode furtherincludes a plurality of trenches extending into the semiconductor bodyfrom the first main surface. A first group of the plurality of trenchesincludes a first trench electrode. The first trench electrode issubdivided into at least a first part and a second part. A conductanceper unit length of the first part along a longitudinal direction of thefirst trench electrode is by at least a factor of 1000 smaller than aconductance per unit length of the second part along the longitudinaldirection of the first trench electrode. The second part is electricallycoupled to the anode pad area via the first part.

Another example of a diode according to the present disclosure includesa semiconductor body having a first main surface and a second mainsurface opposite to the first main surface. The diode further includesan anode region and a cathode region. The anode region is arrangedbetween the first main surface and the cathode region. An anode pad areais electrically connected to the anode region. The diode furtherincludes a plurality of trenches extending into the semiconductor bodyfrom the first main surface. A first group of the plurality of trenchesincludes a first trench electrode. The first trench electrode iselectrically coupled to the anode pad area via an anode wiring line anda resistor.

Another example of a diode according to the present disclosure includesa semiconductor body having a first main surface and a second mainsurface opposite to the first main surface. The diode includes an anoderegion and a cathode region. The anode region is arranged between thefirst main surface and the cathode region. An anode pad area iselectrically connected to the anode region. The diode further includes aplurality of trenches extending into the semiconductor body from thefirst main surface. A first group of the plurality of trenches includesa first trench electrode. At least one resistive element is coupled inseries between the first trench electrode of each trench of theplurality of trenches and the anode pad area. The diode is configured toconduct current in an on-state in a forward direction and to blockcurrent in an off-state, wherein the diode is configured to switch fromthe off-state to the on-state during a switching time, wherein the atleast one resistive element is configured such that a potential of eachfirst trench electrode of the plurality of trenches is deviating from apotential of the anode pad area during the switching time by at least 2Vfor at least 30% of the switching time.

Those skilled in the art will recognize additional features andadvantages upon reading the following detailed description and onviewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the embodiments and are incorporated in and constitutea part of this specification. The drawings illustrate embodiments ofsemiconductor devices, e.g. vertical power semiconductor devices andtogether with the description serve to explain principles of theembodiments. Further embodiments are described in the following detaileddescription and the claims.

FIGS. 1A to 1E are schematic plan and cross-sectional views forillustrating an example of a diode including a resistive couplingbetween a trench electrode and an anode pad area.

FIGS. 2A to 2C, 3 and 4 are schematic plan and cross-sectional views forillustrating other examples of a diode including a resistive couplingbetween a trench electrode and an anode pad area.

FIG. 5 is a schematic cross-sectional view illustrating a semiconductordevice including a diode and a switching device connected in parallel.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof and in which are shownby way of illustrations specific embodiments in which the invention maybe practiced. It is to be understood that other embodiments may beutilized and structural or logical changes may be made without departingfrom the scope of the present invention. For example, featuresillustrated or described for one embodiment can be used on or inconjunction with other embodiments to yield yet a further embodiment. Itis intended that the present invention includes such modifications andvariations. The examples are described using specific language, whichshould not be construed as limiting the scope of the appending claims.The drawings are not scaled and are for illustrative purposes only. Forclarity, the same elements have been designated by correspondingreferences in the different drawings if not stated otherwise.

The terms “having”, “containing”, “including”, “comprising” and the likeare open, and the terms indicate the presence of stated structures,elements or features but do not preclude the presence of additionalelements or features. The articles “a”, “an” and “the” are intended toinclude the plural as well as the singular, unless the context clearlyindicates otherwise.

The term “electrically connected” may be a permanent electricalconnection between elements, for example a permanent direct-currentcontact between the respective elements or a low-resistive connectionvia a metal and/or heavily doped semiconductor material. The term“electrically coupled” may include that one or more intervening controlor resistive element(s) adapted for signal and/or power transmission maybe arranged between the electrically coupled elements, for example,elements such as switches which are controllable to temporarily providean electrical connection in a first state and a high-resistive electricdecoupling in a second state, or resistors. Electrically coupledelements may also be electrically connected, for example. An ohmiccontact is a non-rectifying electrical junction with a substantiallinear current-voltage characteristic.

Ranges given for physical dimensions include the boundary values. Forexample, a range for a parameter y from a to b reads as a≤y≤b. Aparameter y with a value of at least c reads as c≤y and a parameter ywith a value of at most d reads as y≤d.

The term “on” is not to be construed as meaning only “directly on”.Rather, if one element is positioned “on” another element (e.g., a layeris “on” another layer or “on” a substrate), a further component (e.g., afurther layer) may be positioned between the two elements (e.g., afurther layer may be positioned between a layer and a substrate if thelayer is “on” said substrate).

An example of a diode may include a semiconductor body having a firstmain surface and a second main surface opposite to the first mainsurface. The semiconductor body may include an anode region and acathode region. The anode region may be arranged between the first mainsurface and the cathode region. An anode pad area may be electricallyconnected to the anode region. A plurality of trenches may extend intothe semiconductor body from the first main surface. A first group of theplurality of trenches may include a first trench electrode. A secondgroup of the plurality of trenches may include a second trenchelectrode. The first trench electrode may be electrically coupled to theanode pad area via an anode wiring line and the second trench electrode.In a top view, the plurality of trenches may be formed within the diodearea. The plurality of trenches may be directly surrounded bysemiconductor regions forming the p-n-diode.

The diode may be a vertical diode device having a current flow between afirst terminal, e.g. an anode terminal, at the first main surface and asecond terminal, e.g. a cathode terminal, at a second main surfaceopposite to the first main surface. The diode may be a freewheelingdiode. The freewheeling diode may be part of a semiconductor switchingcircuit, e.g. a half-bridge. The diode may be configured to conductcurrents of more than 1 A or more than 10 A or even more than 30 A andmay be further configured to block voltages between anode and cathodeterminals in the range of several hundreds of up to several thousands ofvolts, e.g. 400 V, 650V, 1.2 kV, 1.7 kV, 3.3 kV, 4.5 kV, 5.5 kV, 6 kV,6.5 kV. The blocking voltage may correspond to a voltage class specifiedin a datasheet of the diode, for example.

The semiconductor body may include or consist of a semiconductormaterial from the group IV elemental semiconductors, IV-IV compoundsemiconductor material, III-V compound semiconductor material, or II-VIcompound semiconductor material. Examples of semiconductor materialsfrom the group IV elemental semiconductors include, inter alia, silicon(Si) and germanium (Ge). Examples of IV-IV compound semiconductormaterials include, inter alia, silicon carbide (SiC) and silicongermanium (SiGe). Examples of III-V compound semiconductor materialinclude, inter alia, gallium arsenide (GaAs), gallium nitride (GaN),gallium phosphide (GaP), indium phosphide (InP), indium gallium nitride(InGaN) and indium gallium arsenide (InGaAs). Examples of II-VI compoundsemiconductor materials include, inter alia, cadmium telluride (CdTe),mercury-cadmium-telluride (CdHgTe), and cadmium magnesium telluride(CdMgTe). For example, the semiconductor body may be a magneticCzochralski, MCZ, or a float zone (FZ) or an epitaxially depositedsilicon semiconductor body.

The first main surface may be a level at an interface between thesemiconductor body and a wiring area above the semiconductor body at afirst side of the semiconductor body. Likewise, the second main surfacemay be a level at an interface between the semiconductor body and awiring area, e.g. rear side contact, above the semiconductor body at asecond side of the semiconductor body.

The anode region may include one or a plurality of anode sub-regionsmerged with one another. The anode region may have a first conductivitytype, e.g. p-type. The anode sub-regions may differ, at least partly,from one another with respect to one or more of, doping concentrationprofile, doping concentration species, vertical and/or lateralextension. For example the anode region or the anode sub-regions may beformed by a diffusion and/or ion implantation process, for example. Forexample, the anode region may include a p⁺-doped anode contact regionadjacent to the first main surface and one or more p-doped anodesub-regions extending along the vertical direction deeper into thesemiconductor body than the anode contact region, for example.

The cathode region may include one or a plurality of cathode sub-regionsmerged with one another. The cathode region may have a secondconductivity type, e.g. n-type. The cathode sub-regions may differ, atleast partly, from one another with respect to one or more of, dopingconcentration profile, doping concentration species, vertical and/orlateral extension. For example the cathode region or the cathodesub-regions may be formed by a diffusion and/or ion implantationprocess, for example. For example, the cathode region may include ann⁻-doped drift region, an n-doped field stop region and an n⁺-dopedcathode contact region adjacent to the second main surface. An impurityconcentration in the drift region may gradually or in steps increase ordecrease with increasing distance to the first main surface at least inportions of its vertical extension. According to other examples theimpurity concentration in the drift region may be approximately uniform.For diodes based on silicon, a mean impurity concentration in the driftregion may be between 5×10¹² cm⁻³ and 1×10¹⁵ cm⁻³, for example in arange from 1×10¹³ cm⁻³ to 2×10¹⁴ cm⁻³. In the case of diodes based onSiC, a mean impurity concentration in the drift region may be between5×10¹⁴ cm⁻³ and 1×10¹⁷ cm⁻³, for example in a range from 1×10¹⁵ cm⁻³ to2×10¹⁶ cm⁻³. A vertical extension of the drift region may depend onvoltage blocking requirements of the diode, e.g. a specified voltageclass. When operating the diode in voltage blocking mode, a space chargeregion may vertically extend partly or totally through the drift regiondepending on the blocking voltage applied to the diode. When operatingthe diode at or close to the specified maximum blocking voltage, thespace charge region may reach or penetrate into the field stop region.The field stop region is configured to prevent the space charge regionfrom further reaching to the cathode terminal at the second main surfaceof the semiconductor body. In this manner, the drift region may beformed using desired low doping levels and with a desired thicknesswhile achieving soft switching for the diode thus formed.

A pn-junction may be formed between the anode region and the cathoderegion.

The anode pad area may be part of one wiring level of a wiring areaabove the first main surface. The wiring area may include one or morethan one wiring levels, e.g. two, three, four or even more wiringlevels. Each wiring level may be formed by a single one or a stack ofconductive layers, e.g. metal layer(s) or doped layers, e.g. highlydoped semiconductor layers such as highly doped polycrystalline silicon.The wiring levels may be lithographically patterned, for example.Between stacked wiring levels, an intermediate dielectric may bearranged. One or more contact plugs or contact lines may be formed inopenings of the intermediate dielectric to electrically connect parts,e.g. metal lines or contact areas or pads, of different wiring levels toone another. In case of multiple wiring levels, the anode pad area maybe located furthest away from the first main surface, e.g. in anoutermost wiring level with respect to the first main surface. Forexample, the anode pad area may be arranged above the anode region.Contacts, e.g. plugs and/or contact lines may conduct a diode currentalong the vertical direction between the anode pad area and the anoderegion in the semiconductor body, for example.

For example, all or some parts of each of the plurality of trenches ofthe first and second group may be stripe-shaped. Stripe-shaped parts ofthe trenches of the first and second group may extend in parallel alonga longitudinal direction. For example, the trench electrode in each ofthe first group and second group of the plurality of trenches may beelectrically insulated from a surrounding part of the semiconductorbody, e.g. from the anode region, by a trench dielectric. The trenchdielectric may include one layer or a combination of layers, e.g. alayer stack of dielectric layers, for example oxide layers such asthermal oxide layers or deposited oxide layers, e.g. undoped silicateglass (USG), phosphosilicate glass (PSG), boron silicate glass (BSG),borophosphosilicate glass (BPSG), nitride layers, high-k dielectriclayers or low-k dielectric layers. The trench electrode in each of thefirst group and second group of the plurality of trenches may includeone electrode material or a combination of electrode materials, forexample a doped semiconductor material (e.g. a highly dopedsemiconductor material) such as doped polycrystalline silicon, metal ormetal compounds. The plurality of trenches of the first group and thesecond group may, at least partly, be concurrently formed, e.g. bycommon etch process(es). Likewise, also the trench electrode and/or thetrench dielectric of the first group and the second group may, at leastpartly, be concurrently formed, e.g. by common layer depositionprocess(es). The electrodes in the plurality of trenches may act asfield-plates configured to protect the anode from high electric fieldstrengths that may limit diode switching ruggedness and prevent afurther lowering of the anode efficiency, for example.

Other than in an active area of IGBTs or MOSFETs (metal oxidesemiconductor field effect transistors) where n-doped and p-dopedregions, e.g. source and body, are electrically connected to a loadterminal via the first main surface, the anode pad area may beelectrically connected to a semiconductor region of one conductivitytype only, e.g. the anode region. The active area may be an area at thefirst main surface of the diode where a load current can flow throughthe first main surface between the semiconductor body and the wiringarea, for example. The diode may include areas at the first main surfacethat differ from the active area, e.g. an edge termination area thatpartly or fully surrounds the active area. Since pn-junctions within thesemiconductor body, e.g. the pn-junction between the cathode region andthe anode region, may terminate at edge zones of the semiconductor body,this edge effect may limit the device breakdown voltage below the idealvalue that is set by the parallel plane junction.

The anode wiring line may be arranged at or close to an edge of theactive area. For example, the anode wiring line may be laterally spacedfrom the anode pad area. Although the first trench electrode in thefirst group of the trenches may at least in part be arranged directlybelow the anode pad area, the first trench electrode is electricallycoupled to the anode pad area via the anode wiring line and the secondtrench electrode instead of being directly electrically connected to theanode pad area by a contact above the first trench electrode. Thisprovides a resistive coupling of the first trench electrode to the anodepad such that a higher ohmic resistance is provided between the firsttrench electrode and the anode pad compared to a direct connection ofthe first trench electrode. Thus, the current from the first trenchelectrode is forced to flow along a longitudinal extension of the secondtrench electrode thereby increasing the resistance. Resistively couplingthe first trench electrode to the anode pad area may allow for improvinga tradeoff between diode ruggedness and forward recovery voltage bylimiting a displacement current flow to the first trench electrodes.This may counteract a charging of the parasitic capacitance of thetrenches, and thus, to reduce a prolongation of the forward recoveryphase. Apart from resistively coupling the first trench electrodes tothe anode pad area via a second trench electrode, other measures forresistive coupling may be applied as will be described in examplesbelow, e.g. resistive coupling via a resistor, e.g. a polycrystallinesilicon resistor, in the wiring area above the semiconductor body,resistive coupling via a resistor on a substrate different from thesemiconductor body, resistive coupling via a resistor implemented bynarrowing a cross-section of the trench electrode in the trenches, forexample.

For example, the anode wiring line and the anode pad area may beseparate parts of a patterned wiring layer. For example, the anodewiring line and the anode pad area may correspond to one wiring level ofthe wiring area above the first main surface.

For example, a ratio between a number of trenches in the first group anda number of trenches in the second group may range from 100 to 100,000.The ratio may allow for adjusting a voltage drop of a resistor causingthe resistive coupling between the first trench electrode and the anodepad area, for example. In some embodiments, a longitudinal extension ofthe first trench electrode and the second trench electrode may haveapproximately the same value.

For example, the anode wiring line may laterally surround at least aquarter or half of a circumference of the anode pad area. For thisexample, some or all of the trenches of the first group may beelectrically connected to the anode wiring line at one end of thetrenches. Reducing the degree of circulation of the anode pad area bythe anode wiring line may allow for implementing an area efficientresistive coupling between the anode pad area and the first trenchelectrode, for example.

For example, the second trench electrodes may be connected in parallelbetween the anode wiring line and the anode pad area. A total resistanceof the second trench electrodes connected in parallel multiplied by thetotal capacitance of the first trench electrodes is in a range between100 Ohm×nF and 100 Ohm×μF. The total capacitance may depend on thepermittivity of the oxide material, the thickness of the insulatingdielectric material (e.g. oxide material) of the trenches and theoverall area of the insulating dielectric material opposing thesemiconductor material and the trench electrodes. In some embodiments,the total capacitance may be calculated according to the platecapacitance formula C=ε A/d, wherein ε is the permittivity of thematerial of the insulating dielectric layer, A is the overall area ofthe insulating dielectric material opposing on one side thesemiconductor material and on the other the trench electrodes and d isthe thickness of the insulating dielectric layer.

For example, a conductance per unit length of the second trenchelectrode along a longitudinal direction of the plurality of trenchesmay be smaller than a conductance per unit length of the first trenchelectrode along the longitudinal direction of the plurality of trenches.For example, a material of the second trench electrode may have a largerelectrical resistivity than a material of the first trench electrode.For example, material or material combinations of the first trenchelectrode and the second trench electrode may differ. As an alternativeor in addition, a same semiconductor material may be used for the firsttrench electrode and the second trench electrode, e.g. polycrystallinesilicon, but a doping concentration of the semiconductor material of thefirst trench electrode may be larger than a doping concentration of thesemiconductor material of the second trench electrode. As an alternativeor in addition, a cross-sectional area of the second trench electrode,perpendicular to the longitudinal direction of the trenches, may atleast partly, e.g. in at least some segments of the second trenchelectrode along the longitudinal direction, be smaller than across-sectional area of the first trench electrode.

Another example of a diode may include a semiconductor body having afirst main surface and a second main surface opposite to the first mainsurface. The diode may include an anode region and a cathode region. Theanode region may be arranged between the first main surface and thecathode region. An anode pad area may be electrically connected to theanode region. The diode may include a plurality of trenches extendinginto the semiconductor body from the first main surface. A first groupof the plurality of trenches may include a first trench electrode. Thefirst trench electrode may be subdivided into at least a first part anda second part. A conductance per unit length of the first part along alongitudinal direction of the first trench electrode may be by a factorof at least 1000 smaller than a conductance per unit length of thesecond part along the longitudinal direction of the first trenchelectrode. The second part is electrically coupled (e.g. DC-connected)to the anode pad area via the first part.

Similar to the second trench electrode in the trenches of the secondgroup described in the above examples, the second part of the firsttrench electrode may allow for a resistive coupling between the firstpart of the first trench electrode and the anode pad area.

For example, a material of the first part of the first trench electrodemay have a larger electrical resistivity than a material of the secondpart of the first trench electrode. For example, a material or materialcombinations of the first part of the first trench electrode and thesecond part of the first trench electrode may differ. As an alternativeor in addition, a semiconductor material may be used for the first partof the first trench electrode and for the second part of the firsttrench electrode, e.g. polycrystalline silicon, but a net dopingconcentration of the semiconductor material of the first part of thefirst trench electrode may be smaller than a net doping concentration ofthe semiconductor material of the second part of the first trenchelectrode. As an alternative or in addition, a cross-sectional area ofthe first part of the first trench electrode perpendicular to thelongitudinal direction of the trenches may at least partly be smallerthan a cross-sectional area of the second part of the first trenchelectrode. The smaller cross-sectional area in the first part may beobtained due to a smaller lateral and/or vertical extent (width and/orheight) in at least one segment of the first part of the first trenchelectrode compared to the second part of the first trench electrode.

For example, a lateral extent of the first part along the longitudinaldirection of the first trench electrode may be smaller than a lateralextent of the second part along the longitudinal direction of the firsttrench electrode.

Another example of a diode may include a semiconductor body having afirst main surface and a second main surface opposite to the first mainsurface. The diode may further include an anode region and a cathoderegion. The anode region may be arranged between the first main surfaceand the cathode region. An anode pad area may be electrically connectedto the anode region. A plurality of trenches may extend into thesemiconductor body from the first main surface. A first group of theplurality of trenches may include a first trench electrode. The firsttrench electrode may be electrically coupled to the anode pad area viaan anode wiring line and a resistor.

For example, the resistor may be arranged on a substrate different fromthe semiconductor body. For example, the substrate may be a printedcircuit board or another chip. The diode in the semiconductor body andthe resistor on the substrate may be electrically connected by anysuitable connection technique, e.g. bond wires, solder balls, plug andsocket contacts.

For example, the anode wiring line may merge into an auxiliary anode padarea over the semiconductor body, and a first bond wire electrically mayconnect auxiliary anode pad area and a first end of the resistor on thesubstrate.

For example, the resistor may be arranged in a wiring area over thefirst main surface. For example, the resistor may be formed in a firstwiring level over the first main surface, e.g. a wiring level closest tothe first main surface. The resistor may be formed by polycrystallinesilicon.

For example, a third group of the plurality of trenches may include athird trench electrode. The third trench electrode may be electricallyconnected to the anode pad area via a contact arranged in a part of thefirst main surface where the third trench electrode and the anode padarea overlap one another.

Other than the first trench electrode of the first group which isresistively coupled to the anode pad area, the third trench electrode inthe trenches of the third group may be electrically connected to theanode pad area by contacts arranged between the anode pad area and thethird trench electrode. This may allow for a low-resistive connection ofthe third trench electrode to the anode pad area such that a lower ohmicconnection is provided between the third trench electrode and the anodepad area compared to the higher resistive connection of the first trenchelectrode to the anode pad area. Provision of the third trench electrodemay allow for protecting the anode from high electric field strengthsthat may limit diode switching ruggedness, for example.

For example, the plurality of trenches may extend into the anode region,or may extend through the anode region and into the cathode region, e.g.a drift region of the cathode region.

Another example of a diode may include a semiconductor body having afirst main surface and a second main surface opposite to the first mainsurface. The diode may include an anode region and a cathode region. Theanode region may be arranged between the first main surface and thecathode region. An anode pad area may be electrically connected to theanode region. A plurality of trenches may extend into the semiconductorbody from the first main surface. A first group of the plurality oftrenches may include a first trench electrode. At least one resistiveelement may be electrically coupled in series between the first trenchelectrode of each trench of the plurality of trenches and the anode padarea. The diode is configured to conduct current in an on-state in aforward direction and to block current in an off-state. The diode isfurther configured to switch from the off-state to the on-state during aswitching time, wherein the at least one resistive element is configuredsuch that a potential of each first trench electrode of the plurality oftrenches is deviating from a potential of the anode pad area during theswitching time by at least 2V for at least 30% of the switching time.Providing the resistive element for a trench diode as described aboveallows an effective improvement of a tradeoff between diode ruggednessand forward recovery voltage by limiting a displacement current flow tothe first trench electrodes. This may counteract a charging of theparasitic capacitance of the trenches, and thus, to reduce aprolongation of the forward recovery phase.

The switching time can be determined by a time interval between thesteady off-state and the steady on-state of the diode.

For example, the at least one resistive element is configured such thatthe potential of each first trench electrode of the plurality oftrenches is deviating from the potential of the anode pad area duringthe switching by not more than 15 V for at least 30% of the switchingtime.

For example, the at least one resistive element may be configured suchthat the potential of each first trench electrode of the plurality oftrenches is deviating from the potential of the anode pad area after atime interval of 5 μs from switching by not more than 200 mV.

A resistivity of a resistor for resistively coupling the trenchelectrode to the anode pad area may range from 1 Ohm to 1 kOhm, forexample.

Another example of the present disclosure relates to a semiconductordevice. The semiconductor device includes the diode as described in theexamples above or further below. The semiconductor device furtherincludes a power transistor such as a reverse conducting insulated gatebipolar transistor, RC-IGBT. The diode and the RC-IGBT may beelectrically connected in parallel. For example, the cathode region ofthe diode and the emitter of the RC-IGBT may be electrically connected.Likewise, the anode region of the diode and the collector of the RC-IGBTmay be electrically connected. A transistor cell array of the RC-IGBTmay at least partly surround the diode according to one example.

For example, the anode pad area of the diode and a source contact areaof the RC-IGBT merge with one another. For example, the anode pad areaof the diode and the source contact area may be formed by a continuouspad area of a wiring level, e.g. an outermost wiring level, of a wiringarea. One or more bond wires may be formed on the continuous pad area.The continuous pad area may at least partly cover an active area of thediode and an active area of the RC-IGBT.

The examples and features described above and below may be combined.

In the following, further examples of semiconductor devices areexplained in connection with the accompanying drawings. Functional andstructural details described with respect to the examples above shalllikewise apply to the exemplary embodiments illustrated in the figuresand described further below.

FIG. 1A is a schematic plan view illustrating an example of a diode 100.FIG. 1B is a schematic cross-sectional view along intersection line AAof FIG. 1A. FIG. 1C is a schematic cross-sectional view alongintersection line BB of FIG. 1A. FIG. 1D is a schematic cross-sectionalview along intersection line CC of FIG. 1A.

Referring to the schematic views of FIGS. 1A to 1D, the diode 100includes a plurality of trenches 114 extending from a first main surface104 into a semiconductor body 102. A first group 1141 of the pluralityof trenches 114 includes a first trench electrode 1161. A second group1142 of the plurality of trenches 114 includes a second trench electrode1162. In a plan view, the first group 1141 of the plurality of trenchesand the second group 1142 of the plurality of trenches may be locatedwithin an area of the diode. Between the first group 1142 of theplurality of trenches and the second group 1142 of the plurality oftrenches other trenches may be arranged. Trench dielectrics 1171, 1172electrically separate the trench electrodes 1161, 1162 from asurrounding part of the semiconductor body 102.

The first trench electrode 1161 is electrically coupled to an anode padarea 110, e.g. an anode terminal of a vertical diode such as afreewheeling diode, via an anode wiring line 112 and the second trenchelectrode 1162. The anode wiring line 112 and the second trenchelectrode 1162 are electrically connected in series between the anodepad area 110 and the first trench electrode 1161. In the figures,contacts 120 provide an electric contact between regions of thesemiconductor body 104 and a first wiring level and/or an electriccontact between electrodes in the trenches 114 and the first wiringlevel. The first wiring level may include for example the anode wiringline 112 or the anode pad area 110. An intermediate dielectric 118 isarranged between the first wiring level and the semiconductor body 104.The contacts 120 may correspond to a conductive filling within holes ofthe intermediate dielectric 118. For example, the contacts 120 may becontact plugs or contact lines.

The diode 100 further includes an anode region 108 and a cathode region109. Mesa regions 122 are each confined along a lateral direction x byneighboring two of the trenches 114. In the examples illustrated inFIGS. 1A to 1D, the anode region 108 is formed in the mesa regions 122.In some embodiments a part of the cathode region 109 may also be formedin the mesa regions 122. According to other examples, the anode region108 may extend up to or below a bottom side of the mesa regions 122.Apart from the trenches 114 illustrated in the schematic views of FIGS.1A to 1D, additional trenches may be arranged, e.g. between the trenches114 of the first group 1141 and the trenches 114 of the second group1142. The cathode region 109 is electrically connected to a cathodeterminal 124, e.g. a metal layer or metal layer stack, at a second mainsurface 106 of the semiconductor body 102.

As is schematically illustrated in the cross-sectional view of FIG. 1C,the anode region 108 in the mesa region 122 may be electricallyconnected to the anode pad area 110 via contact 120.

As is schematically illustrated in the cross-sectional view of FIG. 1Din combination with the cross-sectional view of FIG. 1B, the firsttrench electrode 1161 is electrically coupled to the anode pad area 110via the anode wiring line 112 and the second trench electrode 1162.Contacts 120 formed between the first trench electrodes 1161 and theanode wiring line 112 provide a current from the first trench electrode1161 to the anode wiring line 112. Furthermore, contacts between thesecond trench electrodes 1162 and the anode wiring line 112 provide thiscurrent from the anode wiring line 112 to the second trench electrodes1162. Contacts formed between the second trench electrodes 1162 and theanode pad area 110 provides this current to the anode pad area 110. Thisprovides a resistive coupling of the first trench electrode 1161 to theanode pad area 110 such that a higher ohmic resistance is providedbetween the first trench electrode 1161 and the anode pad area 110compared to a direct connection of the first trench electrode 1161.Thus, the current from the first trench electrode 1161 is forced to flowalong a longitudinal extension of the second trench electrode 1162, seee.g. the longitudinal extension between the contacts 120 from the anodewiring line 112 to the second trench electrode 1162 in FIG. 1B and thecontacts 120 from the second trench electrode 1162 to the anode pad area110 in FIG. 1D. Furthermore, a resistance of the electrical connectionof the anode pad area 110 via the contacts 120 to the anode area 108 islower than a resistance of the electrical connection of the anode padarea to the first trench electrodes 1161.

Referring to the schematic cross-sectional view of FIG. 1E, the diode100 may further include, e.g. between the trenches 114 of the firstgroup 1141 and the trenches 114 of the second group 1142 illustrated inFIG. 1C, a third group 1143 of the plurality of trenches 114. Trenches114 of the third group 1143 include a third trench electrode 1163 and atrench dielectric 1173. Other than the first trench electrodes 1161 ofthe first group 1141 of the trenches 114 which are resistively coupledto the anode pad area 110 by the second trench electrodes 1162 of thesecond group 1142 of the trenches 114 (see e.g. FIG. 1A), the thirdtrench electrode 1163 in the trenches 114 of the third group 1143 areelectrically connected to the anode pad area 110 by contacts 120arranged between the anode pad area 110 and the third trench electrode1163. This allows for a low-resistive connection of the third trenchelectrode 1163 to the anode pad area 110 such that a lower ohmicconnection is provided between the third trench electrode 1163 and theanode pad area 110 compared to the higher resistive connection of thefirst trench electrode 1161 to the anode pad area 110. Provision of thethird trench electrode 1163 may allow for protecting the anode from highelectric field strengths that may limit diode switching ruggedness, forexample.

Various layouts of the trenches 114 may be implemented in an active areaof the diode 100.

For example, mesa regions 122 may be confined along the lateraldirection x by a trench 114 of the first group 1141 of trenches 114 andany one of a trench 114 of the second group 1142, or of the third group1143. Likewise, mesa regions 122 may be confined along the lateraldirection x by a trench 114 of the second group 1142 of trenches 114 andany one of a trench 114 of the first group 1141, or of the third group1143.

A further example of a diode 100 is illustrated in the schematic planviews of FIG. 2A, 2B and the schematic cross-sectional view of FIG. 2C.

Similar to the previous examples, the diode 100 includes a plurality oftrenches 114 extending into a semiconductor body 102 from a first mainsurface 104, wherein a first group 1141 of the plurality of trenches 114includes a first trench electrode 1161.

The first trench electrode 1161 is subdivided into at least a first part1261 and a second part 1262. A conductance per unit length of the firstpart 1261 along a longitudinal direction y of the first trench electrode1161 is lower than a conductance per unit length of the second part 1262along the longitudinal direction y of the first trench electrode 1161.

The second part 1262 of the first trench electrode 1161 is electricallycoupled to the anode pad area 110 via the first part 1261. In theschematic view of FIG. 2A, the anode pad area 110 is schematicallyillustrated by a terminal. The first part 1261 may be electricallyconnected to an anode wiring line a contact, or may be directlyconnected to the anode pad area by a contact, for example.

The diode 100 further includes an anode region 108 in a mesa region 122bounded by trenches 114 of the first group 1141.

Referring to the schematic plan view of FIG. 2B, a width w1 of the firsttrench electrode 1161 at the first main surface 104 in the first part1261 is smaller than a width w2 in the second part 1262. This allows fora decrease of a conductance per unit length of the first trenchelectrode 1161 in the first part 1261 along the longitudinal direction ycompared with the second part 1262.

In addition or as an alternative to the example of FIG. 2B, theschematic cross-sectional view of FIG. 2C, which is taken along thelongitudinal direction y of the first trench electrode 1161, is oneexample of a diode having a vertical extent h1 of the first trenchelectrode 1161 in the first part 1261 that is smaller than a verticalextent h2 in the second part 1262 by forming the trench 114 of thesecond group 1142 in the first part 1261 more shallow than in the secondpart 1262.

Another example of a diode 100 is illustrated in the schematic planviews of FIG. 3 .

Similar to the previous examples, the diode 100 includes a first group1141 of trenches 114 that includes a first trench electrode 1161.

The first trench electrode 1161 is electrically coupled to an anode padarea 110 via an anode wiring line 112 and a resistor 130 placed on asubstrate 132 different from the semiconductor body 104. The anodewiring line 112 and the resistor 130 are connected in series between theanode pad area 110 and the first trench electrode 1161. Bond wires 1341,1342 may provide an electric connection between an auxiliary anode padarea 136 in the wiring area of the semiconductor body 102 and thesubstrate 132. However, other interconnection technique, e.g. solderbonds or through silicon vias may be used.

Another example of a diode 100 is illustrated in the schematic plan viewof FIG. 4 .

Instead of placing the resistor 130 on a substrate 132 different fromthe semiconductor body 102, the resistor 130 of the diode 100 in FIG. 4is part of the diode 100 and can be arranged, for example, in the wiringarea of diode 100. For example, the resistor 100 may be implemented as apolycrystalline silicon resistor.

An example of a semiconductor device 200 is illustrated in the schematiccross-sectional view of FIG. 5 .

The semiconductor device 200 includes the diode 100 in a first part 1401of the semiconductor body 102. Structural elements of the diode 100 maycorrespond to any of the structural elements or any combination ofstructural elements described with reference to the diodes 100 in theexamples above. The structural elements of the diode 100 in thesemiconductor body 102 are not illustrated in the schematic view of FIG.5 . The semiconductor device 200 further includes a switching device101, e.g. a reverse conducting insulated gate bipolar transistor,RC-IGBT, in a second part 1402 of the semiconductor body 102. Structuralelements of the switching device 101 in the semiconductor body 102 arenot illustrated in the schematic view of FIG. 5 .

The pad area 110 of the diode 100 and a load contact area 111 of theswitching device 101 may be connected and form a common pad area 142.The common pad area 142 is electrically connected to active areas of thediode 100 and of the switching device 101 by contacts 120. The diode 100and the RC-IGBT 101 may be electrically connected in parallel betweenthe common pad area 142 at the first main surface 104 and a loadterminal 125, e.g. metal layer or metal layer stack, at the second mainsurface 106.

The aspects and features mentioned and described together with one ormore of the previously described examples and figures, may as well becombined with one or more of the other examples in order to replace alike feature of the other example or in order to additionally introducethe feature to the other example.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisinvention be limited only by the claims and the equivalents thereof.

What is claimed is:
 1. A diode, comprising: a semiconductor body havinga first main surface and a second main surface opposite to the firstmain surface; an anode region and a cathode region, wherein the anoderegion is arranged between the first main surface and the cathoderegion; an anode pad area electrically connected to the anode region;and a plurality of trenches extending into the semiconductor body fromthe first main surface, wherein a first group of the plurality oftrenches includes a first trench electrode and a second group of theplurality of trenches includes a second trench electrode, wherein thefirst trench electrode is electrically coupled to the anode pad area viaan anode wiring line and the second trench electrode so as to form anelectrical current path between the first trench electrode and the anodepad area that must pass through the second trench electrode.
 2. Thediode of claim 1, wherein the anode wiring line and the anode pad areaare separate parts of a patterned wiring layer.
 3. The diode of claim 1,wherein a ratio between a number of trenches in the first group and anumber of trenches in the second group ranges from 100 to 100,000. 4.The diode of claim 1, wherein the anode wiring line laterally surroundsat least a quarter of a circumference of the anode pad area.
 5. Thediode of claim 1, wherein the second trench electrodes are connected inparallel between the anode wiring line and the anode pad area, andwherein a total resistance of the second group of trench electrodesconnected in parallel multiplied by the total capacitance of the firstgroup of trench electrodes is in a range between 100 Ohm×nF and 100Ohm×μF.
 6. The diode of claim 1, wherein a conductance per unit lengthof the second trench electrode along a longitudinal direction of theplurality of trenches is smaller than a conductance per unit length ofthe first trench electrode along the longitudinal direction of theplurality of trenches.
 7. A semiconductor device, comprising: the diodeof claim 1; and a reverse conducting insulated gate bipolar transistor,RC-IGBT, wherein the diode and the RC-IGBT are electrically connected inparallel.
 8. The semiconductor device of claim 7, wherein the anode padarea of the diode and a source contact area of the RC-IGBT merge withone another.
 9. The diode of claim 1, wherein a resistance of theelectrical connection of the anode pad area to the anode region is lowerthan a resistance of the electrical connection of the anode pad area tothe first trench electrode.
 10. The diode of claim 1, wherein at leastpart of a cross-sectional area of the second trench electrode,perpendicular to the longitudinal direction of the plurality oftrenches, is smaller than a cross-sectional area of the first trenchelectrode.